1. Field of the Invention
The present invention relates to a surge protector for protecting various devices from surges and preventing accidents from occurring.
2. Description of the Related Art
A surge protector is connected to circuits in which electronic devices used in telecommunication equipment (e.g. telephones, facsimiles, modems, etc.); communication lines, power cables, antennas or CRT driving circuits, etc., which are subject to electrical shocks due to abnormal current flow (surge current) or abnormal voltage (surge voltage) such as lightning surge and static charge, to prevent the destruction caused by a thermal damage and shorting of the electronic devices or the printed circuit board, on which the electronic devices are mounted, due to abnormal voltage.
In the related art, the surge protector which is provided with a surge absorbing element having a micro gap has been proposed, for example. The surge protector includes a column-shaped ceramic member coated with a conductive film. A so-called micro gap is formed on the periphery of the column-shaped ceramic member. Both the surge absorbing element, which has a pair of cap-shaped electrodes on both ends of the ceramic member, and a sealing gas is housed in a glass tube. Then, sealing electrodes, having lead wiring lines on both ends of the cylindrical glass tube are sealed by heating at high temperature. Accordingly, this surge protector is an electric discharge surge protector.
In recent years, even in the case of the electric discharge surge protector, the service life thereof has been prolonged. As an example, the surge protector has a SnO2 coating layer, which has a lower volatility than that of cap-shaped electrodes during the discharge, formed on surfaces in which a main discharge of the cap-shaped electrodes is performed. By structures of the surge protector, it is possible to restrain the metal components of the cap-shaped electrodes from sputtering to an inner wall of the glass tube or a micro gap at the main discharge duration. Therefore, the service life of the surge protector is lengthened (For example, see JP-A-10-106712 (page 5, FIG. 1)).
As the size of devices reduces, it can be surface mounted. As an example of the surge protector, the surface mounting type (melph type) surge protector has been proposed. In the surface mounting type surge protector, since sealing electrodes do not have lead wiring lines, when the surge protector is mounted, the sealing electrodes are connected to a circuit board by soldering to be fixed thereto (For example, see JP-A-2000-268934 (FIG. 1)).
As shown in FIG. 12, the surge protector 100 includes a plate-shaped ceramic member 103 having a conductive film 102 divided by a discharge gap 101 in the middle on one surface thereof; a pair of sealing electrodes 105 disposed on both ends of the plate-shaped ceramic member 103; and an cylindrical ceramic member 107 disposed to fit to the pair of sealing electrodes 105 which are disposed on the both ends of the plate-shaped ceramic member 103 and to seal both the plate-shaped ceramic member 103 and a sealing gas 106.
Each of the sealing electrodes 105 includes a terminal electrode member 108, and a conductive leaf spring 109 which is electrically connected to the terminal electrode member 108 to come in contact with the conductive film 102.
However, the conventional surge protector has the following problems. That is, in the conventional surge protector, SnO2 film is formed by means of, for example, a thin film formation method such as a chemical vapor deposition (CVD). However, since the SnO2 film has a weak adherence to the cap-shaped electrode, the SnO2 film characteristics cannot sufficiently be exhibited due to a peeling of the SnO2 film at the main discharge duration.